The hydroformylation reaction, also known as the oxo reaction, is used extensively in commercial processes for the preparation of aldehydes by the reaction of one mole of an olefin with one mole each of hydrogen and carbon monoxide. One use of the reaction is in the preparation of normal- and iso-butyraldehyde from propylene. The normal- and iso-butyraldehydes obtained from propylene are in turn converted into many commercially-valuable chemical products such as, for example, n-butanol, 2-ethyl-hexanol, n-butyric acid, iso-butanol, neo-pentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, the mono-isobutyrate and di-isobutyrate esters of 2,2,4-trimethyl-1,3-pentanediol.
In many cases, a catalyst system containing a Group VIII metal such as rhodium or cobalt is used to catalyze the oxo process. In addition, a phosphorus ligand such as halophosphites, phosphites, and phosphines can be used to regulate the activity of the Group VIII metal. However, many such phosphorus ligands can be degraded and thereby form acids during the oxo process because of degradation reactions involving the ligands. These degradation acids can cause cascading effects and catalyze further degradation of the ligands and lead to a significant loss of the phosphorus ligands.
Accordingly, there is a need in the art for a process for stabilizing phosphorus-containing catalyst systems against degradation in which minimal or no foreign components are to be introduced into the hydroformylation reactor.
The present invention solves this and other problems as will be apparent to those skilled in the art from reading the remainder of the description and the appended claims.